The present invention generally relates to industrial automated material handling, and more particularly relates to methods and apparatus for handling ophthalmic mold parts in a lens manufacturing line. The present invention has particular application to the production of molded ophthalmic lenses such as contact lenses and intraocular lenses, for example.
There are basically two methods of molding a contact lens, full cast molding and spincasting where one surface is molded and the opposite surface is lathed. In full cast molding, a single mold unit for making a single lens comprises a female mold section having a concave optical surface and a male mold section having a convex optical surface. A quantity of liquid lens material is dispensed into the concave optical surface of the female mold section and the male mold section is seated upon the female mold section with the concave and convex surfaces thereof facing one another to form a lens-shaped mold cavity. The joined female and male mold sections form a single mold unit which is subject to a curing cycle (e.g., by thermal or UV radiation) thereby causing polymerization of the lens material in the mold cavity. Once the lens material has cured, the male and female mold sections are separated to retrieve the cured lens. See, for example, U.S. Pat. No. 5,466,147 issued to Bausch and Lomb Incorporated, the entire reference of which is incorporated herein by reference.
Examples of spincasting (also termed centrifugal casting) are disclosed in U.S. Pat. Nos. 3,660,545 and 3,669,089. In conventional spincasting processes, a liquid polymerizable mixture is charged, generally via injection, to a female mold having a concave molding surface, and the mixture is polymerized while the mold is rotated. The polymerizable mixture can be exposed to polymerizing radiation, such as ultraviolet radiation, and/or heated during rotation of the mold to facilitate polymerization. The produced lens has a convex lens surface shaped by the female concave molding surface and the opposite concave lens surface is shaped by centrifugal force generated by rotation of the mold and surface tension of the mixture contained in the mold.
There are many prior art methods of handling the lens mold parts through a lens manufacturing line, whether it be both the female and male parts in a full cast molding operation, or just the female mold parts in a spincasting manufacturing line. The mold parts are typically injection molded in a mold machine and transferred to a mold holder which may advantageously also function as a mold dispenser at the monomer filling station. One prior art mold holder and dispenser is in the form of an elongated cylindrical tube in which the mold parts are stacked one upon the other. The tube has an open top into which the mold parts are deposited by the pick-and-place head of the mold injection mold machine. The tube also has an open bottom which is temporarily closed with a stopper when depositing molds parts into the tube at the top opening thereof. Once a tube is full, a worker manually retrieves the tube from the mold injection station and places it at the monomer fill station. Since each tube is able to hold only about 100 mold parts each, the amount of time a worker spends changing over empty and full tubes to and from the mold depositing station and the monomer fill station is excessive. The tubes also require cleansing in order to be reused which is difficult and time consuming in that the inside surfaces of the cylindrical tube must be scrubbed clean. There therefore remains a need for an improved method of handling mold parts between manufacturing stations which reduces the amount of time on mold part handling and thus provides cost improvement.
The present invention addresses the above deficiencies of the prior art by providing a system for handling mold parts in an ophthalmic lens manufacturing line wherein the mold handling system is adapted to hold a larger amount of mold parts at a time (e.g., preferably on the order of at least about 1000 (one thousand) mold parts) in a single mold holder or cartridge.
In a first aspect of the invention, a mold cartridge is provided which is preferably of a generally rectangular configuration having spaced front and rear walls which define an internal cavity wherein the mold parts are arranged in side-by-side fashion. Since the cavity for the mold parts is of a large, generally planar shape, there is much more space available to hold mold parts than in the prior art design of a cylindrical mold tube.
In another aspect of the invention, the mold parts are automatically deposited into the mold cartridge by a pick-and-place mold transfer head which picks the mold parts from the injection mold machine which makes the mold parts. A mold drop plate is provided which includes features that align with the mold locations of the mold transfer head. Thus, as molds are formed in the injection mold machine, the mold transfer head picks the molds therefrom and deposits them into the drop plate which is configured to relay the mold parts using force of gravity into a mold cartridge in the correct orientation. This continues until the cartridge is full, at which time an operator takes the full cartridge from the mold machine station to the monomer fill station or a waiting area where the molds are allowed to stabilize for a predetermined amount of time. Of course rather than a worker transferring the mold cartridge between stations, this step in the process may also be automated using robotic handling, if desired.
In yet a further aspect of the invention, the mold cartridge is mounted to a fixture for dispensing molds at the monomer fill station. The mold cartridge feeds molds to the fixture which is adapted to direct mold parts exiting from a bottom exit port in the cartridge to an appropriate mold position at the monomer fill station. Since the present invention is useful for a variety of lens manufacturing methods which utilize mold parts (e.g., spincasting, full cast molding and toric cast molding (where one mold part is rotated relative to a mating mold part), the configuration of the monomer fill station likewise may vary.